In an experiment with pea plants, a pure tall plant (TT) is crossed with a pure short plant (tt). The ratio of pure tall plant to pure short plants in $F_2$ generation will be

According to Mendel's experiments, when a pure tall plant (TT) is crossed with a pure short plant (tt), the F1 generation will have all tall plants (Tt). When these F1 plants are self-pollinated, the F2 generation will have a ratio of 3:1 of tall to short plants. This is because the Tt plants can produce two types of gametes, T and t, which combine to form TT, Tt, and tt genotypes in the F2 generation. The TT and Tt genotypes are tall, while the tt genotype is short.